Methods, systems, and computer program products for detecting a surface using a pipette and/or positioning a pipette

ABSTRACT

This invention relates to methods, systems, and computer program products for detecting a surface using a pipette and/or for positioning a pipette.

RELATED APPLICATION INFORMATION

This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/037,650, filed Aug. 15, 2014, U.S. Provisional Application Ser. No. 62/037,652, filed Aug. 15, 2014, U.S. Provisional Application Ser. No. 62/037,659, filed Aug. 15, 2014, and U.S. Provisional Application Ser. No. 62/037,661, filed Aug. 15, 2014, the disclosures of which are hereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

This invention relates to methods, systems, and computer program products, particularly to methods, systems, and computer program products for detecting a surface using a pipette and/or for positioning a pipette.

BACKGROUND

The isolation of individual colonies of micro-organisms, particularly bacteria, is an important procedure in microbiological laboratories. Traditionally, the isolation of bacteria has been performed manually by skilled laboratory technicians who first dispense a microbiological sample onto the surface of a solid growth culture medium, such as agar in a Petri dish, followed by the use of a hand-tool to spread the sample across the surface of the medium, known as “streaking”. However, these laboratory procedures can also be automated.

For both traditional, manual laboratory procedures and automated laboratory procedures, monitoring and/or verifying that a sample volume has been correctly dispensed onto a solid growth culture medium can be important. This is because if a sample has not been correctly dispensed, then it can create the risk of a false negative.

BRIEF SUMMARY

It is noted that aspects described with respect to one embodiment may be incorporated in different embodiments although not specifically described relative thereto. That is, all embodiments and/or features of any embodiments can be combined in any way and/or combination. Moreover, other systems, articles of manufacture, methods, and/or computer program products according to embodiments will be or become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional systems, articles of manufacture, methods, and/or computer program products be included within this description, be within the scope of the present inventive concept, and be protected by the accompanying claims.

Some embodiments are directed to systems, articles of manufacture, methods and/or computer program products for positioning a pipette and/or detecting a surface using a pipette. In some embodiments, operations include positioning a pipette at a first distance above a surface using a first position detector and positioning the pipette at a second distance above the surface using a second position detector that is different from the first position detector, wherein the second distance is less than the first distance. In some embodiments, the second position detector includes a pipette pressure detector and the first position detector uses a metric other than pressure. Some embodiments include, prior to positioning the pipette at the second distance, contacting the surface with a tip of the pipette.

In some embodiments, operations include measuring a pipette pressure at an internal portion of a pipette to generate a plurality of pipette pressure values. Some embodiments include determining a pressure difference relative to at least one previously measured pipette pressure value. Some embodiments include estimating at least one statistical variable corresponding to a rate of change in pipette pressure. In some embodiments, the at least one statistical variable is compared to at least one pipette pressure related threshold. Some embodiments include, responsive to comparing the at least one statistical variable to the at least one pipette pressure related threshold, estimating a pipette position. Some embodiments include, responsive to comparing the at least one statistical variable to the at least one pressure related threshold, determining if the surface has been contacted with the pipette tip.

In some embodiments, measuring the pipette pressure includes measuring the pipette pressure with a liquid and/or gas in a pipette tip attached to the pipette. In some embodiments, measuring the pipette pressure includes measuring the pipette pressure at given time intervals. Some embodiments include measuring the pipette pressure while aspirating gas into a pipette tip attached to the pipette and while the pipette is moving toward a surface and/or the surface is/are moving toward the pipette. In some embodiments, the pipette is moving downward in a z-direction toward the surface. Some embodiments include the pipette aspirating gas at a constant flow rate.

Some embodiments include, prior to estimating the at least one statistical variable, estimating the rate of change in pipette pressure. In some embodiments, estimating the rate of change in pipette pressure includes mathematically weighting the pressure difference to provide a weighted pressure difference. In some embodiments, estimating the rate of change in pipette pressure includes summing the weighted pressure difference with at least one weighted previously calculated rate of change in pipette pressure. In some embodiments, the pressure difference is weighted by about 0% to 49% and the previously calculated rate of change in pipette pressure is weighted by about 51% to about 100%.

In some embodiments, estimating the at least one statistical variable includes estimating an average rate of change in pipette pressure. In some embodiments, estimating the at least one statistical variable includes estimating a ratio relating to the rate of change in pipette pressure. In some embodiments, the ratio relating to the rate of change in pipette pressure includes the rate of change in pipette pressure and the average rate of change in pipette pressure.

In some embodiments, comparing the at least one statistical variable includes comparing the rate of change in pipette pressure to a first pressure related threshold and comparing a statistical variable to a second pressure related threshold. In some embodiments, the at least one pressure related threshold is determined using a given rate of aspiration and/or a given rate of movement. In some embodiments, the statistical variable is a ratio of the rate of change in pipette pressure divided by an average rate of change in pipette pressure. In some embodiments, the first pressure related threshold is a rate of change in pipette pressure threshold and the second pressure related threshold is a pipette pressure ratio threshold. Some embodiments include detecting contact with a surface detected when the rate of change in pipette pressure is less than or equal to the rate of change in pipette pressure threshold and the ratio of the rate change in pipette pressure divided by the average rate of change in pipette pressure is greater than or equal to the pipette pressure ratio threshold.

In some embodiments, estimating the pipette position includes estimating the position of a pipette tip relative to a surface. In some embodiments, estimating the pipette position includes determining that a surface is not in contact with the pipette and, responsive to determining that the surface is not in contact with the pipette, continuing to estimate the pipette position. In some embodiments, estimating the pipette position includes determining that a surface is in contact with the pipette. In some embodiments, determining if the surface has been contacted with the pipette tip includes estimating the position of the pipette tip relative to the surface.

Some embodiments include determining that the surface is in contact with the pipette by determining that the distal orifice of a pipette tip attached to the pipette has sealed with the surface. In some embodiments, determining that the surface is in contact with the pipette includes detecting at least two consecutive data points that indicate contact to the surface with the pipette.

Some embodiments include, responsive to determining that the surface is in contact with the pipette, stopping movement of the pipette toward the surface and adjusting the pipette to a position above the surface. In some embodiments, responsive to determining that the surface is in contact with the pipette, stopping movement of the surface toward the pipette and adjusting the surface to a position below the pipette. Some embodiments include, responsive to determining that the surface is in contact with the pipette, stopping the aspiration of gas.

In some embodiments, operations include aspirating a liquid into the pipette tip and positioning the pipette tip at a first distance above a surface. Some embodiments include moving the pipette toward the surface while aspirating gas into the pipette tip. Some embodiments include measuring pipette pressure at an internal portion of the pipette and collecting pipette pressure data. In some embodiments, measuring pipette pressure at an internal portion of the pipette includes generating a plurality of pipette pressure values. In some embodiments, the pipette pressure data includes the plurality of pipette pressure values. In some embodiments, contact to the surface with the pipette tip is detected using the pipette pressure data.

Some embodiments are directed to systems, articles of manufacture, methods and/or computer program products for verifying dispensing of a fluid from a pipette. In some embodiments, operations include collecting pressure data while dispensing fluid from a pipette tip attached to a pipette. In some embodiments, the pressure data includes a plurality of pressure values measured at an internal portion of the pipette and taken over a given time interval. In some embodiments, the plurality of pressure values includes a maximum pressure value and a minimum pressure value. Some embodiments include estimating a pressure range value between the maximum pressure value and the minimum pressure value. Some embodiments include determining that the fluid included a liquid, responsive to the pressure range value being greater than or equal to at least one threshold. Some embodiments include determining that the fluid did not include a liquid, responsive to the pressure range value being less than the at least one threshold.

In some embodiments, collecting pressure data while dispensing fluid from the pipette tip attached to the pipette includes measuring pipette pressure at given sampling time intervals. Some embodiments include dispensing fluid from the pipette tip attached to the pipette over the given time interval.

In some embodiments, collecting pressure data while dispensing fluid from the pipette tip attached to the pipette includes dispensing the fluid at a given rate. In some embodiments, the given rate is in a range of about 5 μL/sec to about 400 μL/sec.

Some embodiments include, prior to collecting pressure data while dispensing fluid from the pipette tip attached to the pipette, aspirating a gas into the pipette tip and subsequently aspirating a liquid into the pipette tip. In some embodiments, prior to collecting pressure data while dispensing fluid from the pipette tip attached to the pipette, at least a portion of the liquid is dispensed from the pipette tip.

In some embodiments, collecting pressure data while dispensing fluid from the pipette tip attached to the pipette includes dispensing all fluid present in the pipette tip in the given time interval.

In some embodiments, estimating the pressure range value between the maximum pressure value and the minimum pressure value includes subtracting the minimum pressure value from the maximum pressure value to obtain the pressure range value.

Some embodiments include prior to estimating the pressure range value between the maximum pressure value and the minimum pressure value, removing a portion of pressure values from the plurality of pressure values. In some embodiments, the portion of pressure values is a given number of consecutive pressure values. In some embodiments, the portion of pressure values includes the initial pressure value in the plurality of pressure values.

In some embodiments, determining that the fluid did not include a liquid indicates that a dispensing error occurred.

Some embodiments include estimating a pressure area ratio that identifies at least two pressure data curves, each of the at least two pressure data curves corresponding to at least a portion of the plurality of pressure values. In some embodiments, the pressure area ratio is compared to at least one threshold. Some embodiments include determining that the fluid included a sufficient amount of the liquid, responsive to the pressure area ratio being greater than at least one threshold. Some embodiments include determining that the fluid did not include a sufficient amount of the liquid, responsive to the pressure area ratio being less than or equal to at least one threshold.

In some embodiments, estimating the pressure area ratio includes estimating a maximum area corresponding to a pressure data curve that corresponds to the maximum pressure value and the minimum pressure value. In some embodiments, estimating the pressure area ratio includes estimating an actual pressure area corresponding to a pressure data curve that corresponds to the plurality of pressure values. Some embodiments include multiplying the pressure range value by the given time interval to estimate the maximum area. In some embodiments, the given time interval is the number of pressure values in the plurality of pressure values multiplied by the given sampling time interval between consecutive pressure values in the plurality of pressure values.

In some embodiments, estimating the actual pressure area includes summing areas of a plurality of rectangles. In some embodiments, a width of each rectangle of the plurality of rectangles is the given sampling time interval between consecutive pressure values in the plurality of pressure values. In some embodiments, a height of each rectangle of the plurality of rectangles is a midpoint between at least two consecutive pressure values minus the minimum pressure value.

In some embodiments, determining that the fluid did not include a sufficient amount of the liquid indicates that a dispensing error occurred.

Some embodiments are directed to systems, articles of manufacture, methods and/or computer program products for detecting pipette tip integrity. In some embodiments, operations include collecting pressure data while aspirating a gas into a pipette tip attached to a pipette. In some embodiments, the pipette tip includes a filter. In some embodiments, the pressure data includes a plurality of pressure values measured at an internal portion of the pipette and taken over a given time interval. In some embodiments, the plurality of pressure values include a maximum pressure value and a minimum pressure value.

Some embodiments include estimating a pressure range value between the maximum pressure value and the minimum pressure value. In some embodiments, responsive to the pressure range value being greater than or equal to a lower threshold and the pressure range value being less than or equal to an upper threshold, it is determined that the pipette tip attached to the pipette is properly functioning. Some embodiments include, responsive to the pressure range value being less than a lower threshold. In some embodiments, responsive to the pressure range value being greater than an upper threshold, it is determined that the pipette tip attached to the pipette is not properly functioning.

In some embodiments, collecting pressure data while aspirating gas into the pipette tip attached to the pipette includes measuring pipette pressure at given time intervals. Some embodiments include aspirating gas into the pipette tip attached to the pipette over a given time interval.

In some embodiments, collecting pressure data while aspirating gas into the pipette tip attached to the pipette includes aspirating the gas at a given rate of aspiration. Some embodiments include aspirating gas a rate of aspiration in a range of about 300 μL/s to about 700 μL/s.

In some embodiments, collecting pressure data while aspirating gas into the pipette tip attached to the pipette includes aspirating gas into the pipette tip prior to aspirating a liquid into the pipette tip. Some embodiments include collecting pressure data while aspirating a given volume of gas into the pipette tip attached to the pipette.

In some embodiments, estimating the pressure range value between the maximum pressure value and the minimum pressure value includes subtracting the minimum pressure value from the maximum pressure value to obtain the pressure range value.

Some embodiments include that the upper threshold and/or the lower threshold is/are determined using a given rate of aspiration. In some embodiments, the given rate of aspiration is in a range of about 300 μL/sec to about 700 μL/sec. Some embodiments include that the given rate of aspiration is the same as the rate of aspiration for aspirating the gas into the pipette tip attached to the pipette.

Some embodiments include, responsive to the pressure range value being greater than or equal to the lower threshold and the pressure range value being less than or equal to the upper threshold, determining that the pipette tip attached to the pipette is suitable for use.

Some embodiments include, responsive to the pressure range value being greater than or equal to the lower threshold and the pressure range value being less than or equal to the upper threshold, aspirating a liquid into the pipette tip.

Some embodiments include, responsive to the pressure range value being less than the lower threshold or the pressure range value being greater than the upper threshold, removing the pipette tip from the pipette.

Some embodiments include, responsive to the pressure range value being less than the lower threshold or the pressure range value being greater than the upper threshold, determining that the pipette tip is defective, clogged, and/or improperly attached to the pipette.

Some embodiments include, detecting that the pipette tip is defective or without a filter responsive to the pressure range value being less than the lower threshold.

Some embodiments include, detecting that the pipette tip is defective responsive to the pressure range value being greater than the upper threshold. In some embodiments, the pipette tip is a clogged.

In some embodiments, the maximum pressure value is measured at a first point in time and the minimum pressure value is measured at a second point in time and the first point in time is before the second point in time. In some embodiments, the maximum pressure value is measured at a first point in time and the minimum pressure value is measured at a second point in time and the second point in time is before the first point in time.

Some embodiments are directed to systems, articles of manufacture, methods and/or computer program products for detecting a droplet. In some embodiments, operations include estimating a plurality of rate of change in pipette pressure values during a given time interval. Some embodiments include detecting the formation of a droplet at a distal end of a pipette tip attached to a pipette, responsive to at least one of the plurality of rate of change in pipette pressure values being greater than or equal to an upper pressure related threshold and at least one of the plurality of rate of change in pipette pressure values being less than or equal to a lower pressure related threshold.

In some embodiments, estimating the plurality of rate of change in pipette pressure values during the given time interval includes measuring a pipette pressure at an internal portion of a pipette at given sampling time intervals to generate a plurality of pipette pressure values. In some embodiments, estimating the plurality of rate of change in pipette pressure values during the given time interval includes determining a plurality of pressure differences relative to at least one previously measured pipette pressure value. In some embodiments, estimating the plurality of rate of change in pipette pressure values during the given time interval includes mathematically weighting each of the plurality of pressure differences to provide the plurality of rate of change in pipette pressure values.

In some embodiments, mathematically weighting each of the plurality of pressure differences to provide the plurality of rate of change in pipette pressure values includes weighting a most recently determined pressure difference to provide a weighted pressure difference. In some embodiments, mathematically weighting each of the plurality of pressure differences to provide the plurality of rate of change in pipette pressure values includes weighting at least one previously calculated rate of change in pipette pressure value to provide a weighted previously calculated rate of change in pipette pressure value. Some embodiments include summing the weighted pressure difference and the weighted previously calculated rate of change in pipette pressure value. In some embodiments, the most recently determined pressure difference is weighted by about 0% to 49% and the at least one previously calculated rate of change in pipette pressure value is weighted by about 51% to about 100%.

In some embodiments, the plurality of rate of change in pipette pressure values changes over a period of time.

Some embodiments include determining the upper pressure related threshold and/or the lower pressure related threshold using a given rate of dispense.

In some embodiments, the droplet has a volume in a range of about 0.5 μL to about 3.5 μL.

In some embodiments, at least one of the plurality of rate of change in pipette pressure values corresponds to a rate of change in pipette pressure while the pipette is dispensing a gas. In some embodiments, at least one of the plurality of rate of change in pipette pressure values corresponds to a rate of change in pipette pressure while the pipette is dispensing a liquid.

Some embodiments include, responsive to detecting the formation of the droplet, stopping dispensing of liquid from the pipette tip.

In some embodiments, a clog is detected in the pipette tip attached to the pipette. In some embodiments, detecting the clog in the pipette tip attached to the pipette includes determining that a given number of rate of change in pipette pressure values of the plurality of rate of change in pipette pressure values are greater than or equal to a first clog related threshold. In some embodiments, detecting the clog in the pipette tip attached to the pipette includes determining that an updated pressure difference corresponding to a most recently measured pipette pressure value of the plurality of pipette pressure values is greater than a second clog related threshold.

In some embodiments, the given number of rate of change in pipette pressure values of the plurality of rate of change in pipette pressure values corresponds to a given period of time.

Some embodiments include estimating the updated pressure difference. In some embodiments, estimating the updated pressure difference includes selecting a minimum pipette pressure value from the plurality of pipette pressure values and subtracting the minimum pipette pressure value from the most recently measured pipette pressure value of the plurality of pipette pressure values.

In some embodiments, the second clog related threshold corresponds to a cumulative rise in pressure of a given value. Some embodiments include determining the first clog related threshold and/or the second clog related threshold using a given rate of dispense.

Some embodiments include detecting that the pipette tip does not contain a liquid. In some embodiments, detecting that the pipette tip does not contain the liquid includes estimating a plurality of changes in pressure over a given period of time. In some embodiments, detecting that the pipette tip does not contain the liquid further includes determining that a portion of the plurality of changes in pressure indicate no significant change in pressure. In some embodiments, the portion of the plurality of changes in pressure that indicates no significant change in pressure is at least 50%.

In some embodiments, estimating the plurality of changes in pressure over the given period of time includes measuring the pipette pressure at an initial point in time and estimating the plurality of changes in pressure at a given point in time after the initial point in time.

Some embodiments include measuring a pipette pressure at an internal portion of the pipette including a pipette tip attached thereto to generate a plurality of pipette pressure values. In some embodiments, a pressure difference relative to at least one previously measured pipette pressure value is determined. Some embodiments include providing a plurality of pressure difference values. In some embodiments, a portion of the plurality of pressure difference values is compared with an upper pressure related threshold and a lower pressure related threshold. Some embodiments include detecting the formation of a droplet, responsive to determining that at least one pressure difference value of the portion of the plurality of pressure difference values is greater than or equal to the upper pressure related threshold and that at least one pressure difference value of the portion of the plurality of pressure difference values is less than or equal to the lower pressure related threshold.

In some embodiments, comparing the portion of the plurality of pressure difference values with the upper pressure related threshold and the lower pressure related threshold includes comparing a portion of a plurality of rate of change in pipette pressure values with the upper pressure related threshold and the lower pressure related threshold.

Some embodiments include estimating a rate of change in pipette pressure and providing a plurality of rate of change in pipette pressure values. In some embodiments, estimating the rate of change in pipette pressure includes mathematically weighting the pressure difference to provide a weighted pressure difference. In some embodiments, estimating the rate of change in pipette pressure includes summing the weighted pressure difference with at least one weighted previously calculated rate of change in pipette pressure. In some embodiments, the pressure difference is weighted by about 0% to 49% and the previously calculated rate of change in pipette pressure is weighted by about 51% to about 100%.

Some embodiments include measuring the pipette pressure at given sampling time intervals. In some embodiments, measuring the pipette pressure includes measuring the pipette pressure while the pipette is positioned at a given position.

In some embodiments, comparing the portion of the plurality of pressure difference values with the upper pressure related threshold and the lower pressure related threshold includes comparing at least two pressure difference values.

In some embodiments, the plurality of pressure difference values changes over a period of time.

Some embodiments include determining the upper pressure related threshold and/or the lower pressure related threshold using a given rate of dispense.

In some embodiments, the droplet has a volume in a range of about 0.5 μL to about 3.5 μL.

In some embodiments, at least one pressure difference value of the portion of the plurality of pressure difference values corresponds to a pipette pressure while the pipette is dispensing a gas. In some embodiments, at least one pressure difference value of the portion of the plurality of pressure difference values corresponds to a pipette pressure while the pipette is dispensing a liquid.

Some embodiments include, responsive to detecting the formation of the droplet, stopping dispensing of liquid from the pipette tip.

Some embodiments include detecting a clog in the pipette tip attached to the pipette. In some embodiments, detecting the clog in the pipette tip attached to the pipette includes determining that a given number of rate of change in pipette pressure values of the plurality of rate of change in pipette pressure values are greater than or equal to a first clog related threshold. In some embodiments, detecting the clog in the pipette tip attached to the pipette includes determining that an updated pressure difference corresponding to a most recently measured pipette pressure value of the plurality of pipette pressure values is greater than a second clog related threshold.

In some embodiments, the given number of rate of change in pipette pressure values of the plurality of rate of change in pipette pressure values corresponds to a given period of time.

Some embodiments include estimating the updated pressure difference. In some embodiments, estimating the updated pressure difference includes selecting a minimum pipette pressure value from the plurality of pipette pressure values and subtracting the minimum pipette pressure value from the most recently measured pipette pressure value of the plurality of pipette pressure values.

In some embodiments, the second clog related threshold corresponds to a cumulative rise in pressure of a given value. In some embodiments, the first clog related threshold and/or the second clog related threshold is/are determined using a given rate of dispense.

Some embodiments include detecting that the pipette tip does not contain a liquid. In some embodiments, detecting that the pipette tip does not contain a liquid includes estimating a plurality of changes in pressure over a given period of time. In some embodiments, detecting that the pipette tip does not contain the liquid includes determining that a portion of the plurality of changes in pressure indicate no significant change in pressure. In some embodiments, the portion of the plurality of changes in pressure that indicates no significant change in pressure is at least 50%.

In some embodiments, estimating the plurality of changes in pressure over the given period of time includes measuring the pipette pressure at an initial point in time and estimating the plurality of changes in pressure at a given point in time after the initial point in time.

In some embodiments, determining the pressure difference relative to the at least one previously measured pipette pressure includes measuring the pipette pressure at an initial point in time and determining the pressure difference relative to the least one previously measured pipette pressure at a given point in time after the initial point in time. Some embodiments include that the given point in time after the initial point in time corresponds to a volume of gas present in the distal portion of the pipette tip at the initial point in time.

Some embodiments of the present disclosure are directed to computer program products that include a computer readable storage medium having computer readable program code embodied in the medium. The computer code may include computer readable code to perform any of the operations as described herein.

Some embodiments of the present disclosure are directed to a computer system that includes at least one processor and at least one memory coupled to the processor. The at least one memory may include computer readable program code embodied therein that, when executed by the at least one processor causes the at least one processor to perform any of the operations as described herein.

It is noted that aspects of the disclosure described with respect to one embodiment, may be incorporated in a different embodiment although not specifically described relative thereto. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination. These and other objects and/or aspects of the present inventive concept are explained in detail in the specification set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are illustrated by way of example and are not limited by the accompanying figures with like references indicating like elements.

FIG. 1 is a perspective view from the front of an automated streaking apparatus according to some embodiments of the present inventive subject matter.

FIG. 2 is a perspective view from the rear of the apparatus of FIG. 1 according to some embodiments of the present inventive subject matter.

FIG. 3 is a perspective view from above a part of the apparatus of FIG. 1 according to some embodiments of the present inventive subject matter.

FIG. 4 is a perspective view of a pipette pressure detector according to some embodiments of the present inventive subject matter.

FIG. 5 is a flowchart illustrating operations in methods according to some embodiments of the present inventive subject matter.

FIG. 6 is a flowchart illustrating operations in methods according to some embodiments of the present inventive subject matter.

FIG. 7 is a graph of pressure values versus time according to some embodiments of the present inventive subject matter.

FIG. 8 is a flowchart illustrating operations in methods according to some embodiments of the present inventive subject matter.

FIG. 9 is a flowchart illustrating operations in methods according to some embodiments of the present inventive subject matter.

FIG. 10 is a flowchart illustrating operations in systems according to some embodiments of the present inventive subject matter.

FIG. 11 is a block diagram illustrating systems according to some embodiments of the present inventive subject matter.

DETAILED DESCRIPTION

As discussed herein, systems, articles of manufacture, methods, and/or computer program products of the present inventive subject matter may provide an effective and efficient way to detect a surface using a pipette and/or to position a pipette. Some embodiments of the present inventive subject matter may provide the ability to monitor and/or verify that a liquid sample volume is correctly dispensed onto a surface of a target, such as a surface of solid growth culture medium (e.g., agar). Thus, some embodiments of the present inventive subject matter may reduce the risk of a false negative. For example, if a pipette tip is not positioned close enough to a surface, such as a surface of solid growth culture medium (e.g., agar), when the liquid sample in the pipette tip is dispensed from the pipette tip, the liquid sample may not be dispensed or wicked off onto the surface. Instead, the liquid sample may be wicked up onto the side of the pipette tip. Some embodiments of the present inventive subject matter may provide the ability to position a pipette tip attached to a pipette close to a surface without lowering the tip too far such that it scratches or gouges the surface, such as a surface of solid growth culture medium (e.g., agar). Some embodiments of the present inventive subject matter may improve the accuracy of detecting a surface of a target, such as a surface of solid growth culture medium (e.g., agar), compared to other methods of detecting the surface of the target. Thus, some embodiments of the present inventive subject matter may more accurately position a pipette tip attached to a pipette above a surface and may thereby reduce the risk of a false negative. “Liquid” as used herein refers to a sample having a viscosity suitable for aspirating and dispensing using a pipette, but which may include solid particles. In some embodiments, the liquid sample is a biological sample.

In some embodiments, systems, articles of manufacture, methods, and/or computer program products of the present inventive subject matter may be used with and/or in an automated apparatus. The automated apparatus may be an apparatus for positioning a pipette and/or for pipetting a liquid onto a surface of a target, such a surface of solid growth culture medium (e.g., agar). In some embodiments, the automated apparatus may be an apparatus for inoculating and streaking a solid growth culture medium in a plate, such as, for example, the apparatus illustrated in FIGS. 1 and 2.

Reference is now made to FIGS. 1 and 2, which are a perspective view from the front and rear, respectively, of an automated streaking apparatus according to some embodiments of the present inventive subject matter. The apparatus includes a plate supply (indicated by the letter A) that includes a plurality of input plate cassettes 10 (only cassettes 10 a and 10 f are shown) supported on an upper frame (not shown) for the supply of raw plates to the apparatus, together with a plate store (indicated by the letter B) that includes a plurality of output plate cassettes 11 (only cassettes 11 a and 11 f are shown) also supported on the upper frame for the storage of processed plates from the apparatus. Also shown in FIG. 1 is an inoculation and streaking station (indicated by the letter C).

In some embodiments, the plate supply A and the plate store B are supported by the upper frame so as to be in front of a main gantry 12, along which various of operative carriages of the apparatus may move, as will be explained below. The various parts of the inoculation and streaking station C may be supported by a lower frame (not shown).

Operatively engaged for sliding movement along the main gantry 12 is a plate supply carriage 14 a and a plate store carriage 14 b, which form a part of a plate transfer feed mechanism and a plate transfer store mechanism, respectively. These carriages are both configured for movement along the main gantry 12 (in the x direction) to move a plate (16 a or 16 b) from the plate supply A to the inoculation and streaking station C and then to the plate store B. The carriages 14 a, 14 b are also configured to provide movement of a plate 16 a, 16 b along vertical guiderails 18 a, 18 b thereon to raise and/or lower such plate 16 a, 16 b in the z direction to or from the respective cassettes 10 a to 10 f, and 11 a to 11 f and to or from either or both of the dual plate orientation mechanisms 20 a, 20 b.

In this respect, it can be seen that each of the carriages 14 a, 14 b includes a plate support tray 22 a, 22 b upon which the plates 16 a, 16 b rest in transit, the plate support trays 22 a, 22 b being suitably mounted to their respective carriages for the movement described above. In some embodiments, the plates 16 a, 16 b may be supplied and stored in their respective cassettes 10 a-10 f, 11 a-11 f in an inverted orientation, such that their bottoms are uppermost and their lids are lowermost.

Also configured for movement along the main gantry 12 are an inoculating device 30 and a streaking device 40. In some embodiments, both may be mounted upon a suitable carriage for movement along the main gantry in the x direction. The inoculation device 30 may include a pipette robot system controlled so as to be able to access supply 32 of pipette tips and a sample supply system 34 that includes a number of supply tubes 36, and to access a plate work position (one such position shown in FIG. 2 by the letter D) for inoculation purposes. The streaking device 40 may include a streaking robot system controlled so as to be able to access a streaking applicator supply 42 that, in some embodiments, includes four applicator supply cartridges 46 received in four corresponding cartridge holders 44.

In some embodiments, the inoculation and streaking station C of the apparatus includes dual plate work positions D and dual rotation devices 52 a, 52 b for the streaking of dual plates 16 c, 16 d as shown in FIG. 2 in the dual plate work positions D, and dual plate orientation mechanisms 20 a, 20 b, the location of which is indicated in FIGS. 1 and 2 by the reference numerals 50 a and 50 b. While FIG. 2 generally shows de-lidded plates 16 c, 16 d in the plate work positions D underneath dual sensors 54 a, 54 b, FIG. 1 shows dual plates 16 e, 16 f being orientated and de-lidded by the dual orientation mechanisms 20 a, 20 b. It will of course be appreciated that such a dual configuration is not essential for an apparatus in accordance with the present invention, and that single such stations and devices could be used. Indeed, an apparatus that includes three or four or more such stations and devices is also envisaged.

In some embodiments, the inoculating and streaking station C is the general location within the apparatus where the main functions of the apparatus occur, which location is generally centered around the plate work positions D. In some embodiments, the plate work positions D are defined by the physical location in the apparatus of the sensors 54 a, 54 b, which may be rigidly mounted to respective sensor mounting frames 58 a, 58 b. The apparatus may also include dual plate platforms for supporting a plate, although the combination of FIGS. 1 and 2 shows four such platforms, being the dual platforms 60 a, 60 b in the positions shown in FIG. 1, and the platforms 62 a, 62 b shown in FIG. 2. In this respect, these figures each show two platforms (in different positions) simply for the sake of description.

In some embodiments, each cassette 10 a, 11 a may be able to hold multiple plates within their inner chambers. For example, cassette 10 a may hold multiple plates for the purpose of providing raw plates to the apparatus for subsequent processing, and cassette 11 a may hold multiple plates for the purpose of storing processed plates following inoculation and streaking in the apparatus. As can be seen in FIGS. 1 and 2, each of the cassettes 10 a, 11 a also interacts with its respective carriage 14 a, 14 b to capture a plate, from below, on the respective trays 22 a, 22 b due to respective internal engaging and plate release/lock means (not shown).

In some embodiments, the inoculating device 30 of the apparatus of the present invention may be any device that is able to obtain and hold a sample, generally in a liquid form, and transfer that sample to a surface, such as the surface of a medium in a positioned plate. In some embodiments, the inoculating device 30 may be a pipette 31 mounted to a robot system (not shown) so as to be movable in the z-direction, as well as the x- and y-directions along the main gantry 12 as mentioned above. In some embodiments, the pipette 31 may include a pressure transducer configured to monitor pressure and/or vacuum profiles in an internal portion of the pipette 31.

Reference is now made to FIG. 3, which is a perspective view from above a part of the apparatus of FIG. 1 according to some embodiments of the present inventive subject matter. The pipette 31 may include a pipette tip 33 releasably secured thereto. In some embodiments, the pipette tip 33 may include a filter and/or may be disposable. The pipette tip 33 may be releasably secured and/or attached to the pipette 31 in a manner that permits easy disposal of the pipette tip 33, such as disposal after inoculation has been affected. In some embodiments, the pipette 31 may be programmable for aspirating and/or dispensing various sample volumes at given points in time. In some embodiments, the pipette 31 may include a positional height referencing system, such as, but not limited to, a positional height z-direction referencing system. The positional height referencing system may be configured to determine in three dimensional space the height location of the pipette tip 33 relative to the datum level and reference points of a platform, such as platform 60 a, 60 b, 62 a, 62 b, as will be described below, and/or relative to a notional action line.

In some embodiments, the pipette robot system may be configured to move the pipette 31 to access a pipette tip supply 32, which may include a rack of pipette tips 33, to access the biological sample station 34, which may include a rack of sample containers such as sample tubes, to access the plate work position D in the inoculating and streaking station C, and/or to access a tip waste disposal area or chute. The pipette robot system, pipette 31, and/or pipette tip 33 may include suitable tip securing means that is configured for the pipette tip 33 to be secured to the pipette 31. In some embodiments, the pipette robot system, pipette 31, and/or pipette tip 33 may be configured to obtain and hold a sample, to dispense sample, and to dispose of a used pipette tip 33.

Referring again to FIG. 3, FIG. 3 illustrates some of the structures used for operations that may occur in the plate work position D and illustrates a plate platform 60 a with a plate bottom 19 in a centralized and clamped position in the plate work position D. In some embodiments, the plate platform 60 a may include a plate clamping member 75 in the form of three movable lugs operated by a camming device (not shown), which lugs may be configured to function as a plate centralizing means for centralizing the position of the plate bottom 19 on the platform 60 a.

In some embodiments, the plate work position D may include a notional action line fixed in two dimensions (x,y) in a given position, together with a datum level Y (e.g., the surface upon the plate platform 60 a). The action line is herein referred to as being a “notional” action line given that it will not be a visible action line and also will not have a determined position in three dimensional space until the height of the surface 70 of the medium in the plate bottom 19 is determined.

In some embodiments, the plate work position D may include a position detector, such as, for example, 1, 2, 3, 4, or more position detectors. The position detector may be configured and/or used to locate the surface 70 in a plate bottom 19 and/or to detect the z-position of medium in the plate bottom 19. In some embodiments, the position detector may include a sensor 54 a. In some embodiments, the plate work position D may include a datum level Y, which may be the uppermost surface upon the plate platform 60 a. In some embodiments, the sensor 54 a may include an ultrasonic sensing device 55 a having an ultrasonic beam focusing element that is configured to provide a focused beam on the surface 70 and/or within a sensing region that is central to the notional action line. The sensor 54 a may be rigidly mounted via a sensor support arm 58 a, thereby defining the general location of the plate work position D. In some embodiments, the sensor 54 a may be mounted so that it is above the plate work position D and is operatively adjacent the plate bottom 19 held immediately therebelow in the plate platform 60 a, the plate bottom 19 having its surface 70 open upwardly. In some embodiments, the sensor 54 a may be positioned over a plate bottom 19, but may not be positioned over the starting position for dispensing a sample from a pipette tip 33.

In some embodiments, the sensor 54 a may be configured to sense the surface 70 and/or measure the distance to the surface 70. The measured distance may then be referenced to the datum level Y to determine a surface positional reference relative to the datum level Y in one dimension (z) for the surface 70 in the plate bottom 19. In this manner, it will be appreciated that the surface 70 can thus be located in at least the z dimension by virtue of the determination of this surface positional reference. This may effectively determine the height of the medium in the plate bottom 19, at least with reference to that datum level Y. In this respect, and as can be seen in the figures, the datum level Y is a surface that forms a part of the plate platform 60 a upon which the plate is clamped and supported. Therefore, in some embodiments, the determination of the surface positional reference effectively determines the height of the medium with reference to the plate platform 60 a upon which it rests.

In some embodiments, the surface positional reference may be used together with the notional action line to determine the line G in three dimensions (x,y,z) that is representative of a line across the surface 70 in the positioned plate.

In some embodiments, the notional three dimensional action line that is represented by the line G across the surface 70 of the medium in the plate bottom 19 will be specific to the medium in that plate bottom 19 only, and may be a different three dimensional action line compared to the surface of the next plate processed in the plate work position D. In some embodiments, the given (x, y) position of the notional action line is, with reference to the circular plate bottom 19, located such that the notional action line will be a radial line for a circular plate. In some embodiments, this means that the line G, which represents the action line in three dimensions (x, y, z), will also be a radial line.

In some embodiments, once the position of the three dimensional action line G for a medium in a given positioned plate in three dimensional space has been determined, the sample may be deposited onto the surface 70 of the medium along the line G. As used herein, the reference to a sample being dispensed “along” a line or there being inoculation “along” a line, is intended to include a variety of forms of dispensing/inoculation. For example, a sample may be dispensed continuously along the full length of the line, or may be dispensed semi-continuously along the line, such as may be provided by a series of discrete deposits in the form of dots and/or dashes. Similarly, some embodiments include that a sample may be dispensed in a substantially non-linear form.

In some embodiments, the position detector may include a camera. The camera may be configured and/or used to detect the z-position of a pipette tip 33. In some embodiments, the camera and/or sensor 54 a may be used to determine the three dimensional action line G for a medium.

In some embodiments, a pipette pressure detector may be used to determine the surface of medium in a positioned plate. Some embodiments include using a pipette pressure detector to determine the surface of medium in a positioned plate after and/or during a camera and/or sensor 54 a determining the three dimensional action line G for the medium. In some embodiments, the pipette pressure detector may more accurately determine the surface of the medium than the camera and/or sensor 54 a.

In some embodiments, a pipette pressure detector may be used to determine and/or verify dispensing of a fluid from the pipette tip 33 attached to the pipette 31. Some embodiments include detecting that a liquid is/was present in pipette tip 33 after a given amount of the liquid has been dispensed from the pipette tip 33 using a pipette pressure detector. Some embodiments include determining that a sufficient amount of liquid is/was present in the pipette tip 33 after a given amount of the liquid was dispensed from the pipette tip 33 using a pipette pressure detector. Some embodiments include determining and/or verifying dispensing of a fluid from the pipette tip 33 attached to the pipette 31 after the pipette pressure detector has determined and/or detected the surface of medium in a positioned plate. In some embodiments, the fluid is a liquid.

In some embodiments, a pipette pressure detector may be used to detect and/or determine the integrity of the pipette tip 33 attached to the pipette 31. Some embodiments include using the pipette pressure detector to detect and/or determine that the pipette tip 33 is functioning properly and/or is suitable for use. In some embodiments, determining that the pipette tip 33 is suitable for use includes determining that the pipette tip 33 attached to pipette 31 is suitable to aspirate and dispense a liquid. Some embodiments include using the pipette pressure detector to detect and/or determine that the pipette tip 33 is not functioning properly and/or is not suitable for use. In some embodiments, the pipette pressure detector may be used to detect and/or determine the integrity of the pipette tip 33 prior to aspirating a liquid sample into the pipette tip 33 and/or prior to determining the surface of medium in a positioned plate.

In some embodiments, a pipette pressure detector may be used to detect a droplet at the distal end of pipette tip 33 attached to the pipette 31 and/or the formation of a droplet at the distal end of pipette tip 33 attached to the pipette 31. Some embodiments include using the pipette pressure detector to detect a droplet and/or the formation of a droplet at the distal end of pipette tip 33 after the pipette pressure detector has determined the surface of medium in a positioned plate and/or after the pipette 31 has been positioned at a location for dispensing a liquid sample.

In some embodiments, a pipette pressure detector may be used to detect a clog in the pipette tip. In some embodiments, a pipette pressure detector may be used to detect an empty pipette tip (i.e., a pipette tip with no liquid present in the pipette tip).

The pipette pressure detector may include a pressure transducer and a pressure data module. In some embodiments, the pressure transducer and pressure data module may be integrated into a single package. In some embodiments, the pipette pressure detector may be mounted onto the pipette 31 and/or may be integral to the pipette 31. The pressure transducer may be in fluidic communication with an internal portion of the pipette 31 and/or may be built-in to the pipette 31. The pressure data module may receive and/or transmit signals corresponding to a pressure at an internal portion of the pipette 31. Some embodiments include the pressure data module receiving signals from the pressure transducer. In some embodiments, the pressure data module may convert a signal received from the pressure transducer to a different signal and/or signal format, such as, for example, from an analog signal to a digital signal. In some embodiments, the pipette pressure detector may be used to calculate the z-position relative to the surface 70 to move the pipette tip 33 to a desired position before the sample is dispensed from the pipette tip 33.

Some embodiments include using a pipette pressure detector to detect that the surface of a medium in a given plate is at a desired position for dispensing a sample from the pipette tip 33. In some embodiments, the desired position may be over the starting position for dispensing the sample from the pipette tip 33. Some embodiments include dispensing a liquid sample from the pipette tip 33 after a pipette pressure detector has determined the position of the surface of a medium in a given plate relative to the pipette tip 33 and/or after the pipette 31 has been moved to a z-position above the surface.

In some embodiments, while the liquid sample is being dispensed from the pipette tip 33, a pipette pressure detector may detect a droplet and/or the formation of a droplet at the distal end of pipette tip 33 attached to pipette 31. Some embodiments include stopping dispensing of the liquid sample from pipette tip 33 upon detecting the droplet and/or the formation of the droplet at the distal end of pipette tip 33 attached to pipette 31. In some embodiments, after detecting the droplet and/or the formation of the droplet at the distal end of pipette tip 33, the pipette 31 may be moved to a different position, such as, for example, a different position above the surface, and/or a second droplet may be detected at the distal end of pipette tip 33 attached to pipette 31.

In some embodiments, upon dispensing a liquid sample from the pipette tip 33 onto the surface 70 of the medium, a pipette pressure detector may be used to determine and/or verify that a remaining volume and/or a sufficient amount of the liquid sample is/was present in the pipette tip 33. In some embodiments, upon dispensing a liquid sample from the pipette tip 33 onto the surface 70 of the medium, the dispensed liquid may be streaked using the streaking device 40. In some embodiments, a line of spaced apart contact surfaces of a streaking applicator may contact at least a portion of the dispensed liquid, optionally along line G, on the surface 70 of the medium in the plate bottom 19. In some embodiments, the streaking applicator may contact the dispensed liquid and/or medium with a given contact pressure. In some embodiments, the given contact pressure may be suitable for the particular streaking applicator being used, for the composition of the liquid sample, and/or for the particular solid growth medium being used. In some embodiments, the given contact pressure may be such that the liquid is spread when the platform 60 a is rotated and such that the streaking applicator does not undesirably gouge the surface of the medium.

As those of skill in the art will understand and appreciate, the above apparatus described in reference to FIGS. 1-3 is described only to provide an example embodiment in which systems, articles of manufacture, methods, and/or computer program products of the present inventive subject matter may be embodied. The above discussion is not intended to limit the systems, articles of manufacture, methods, and/or computer program products of the present inventive subject matter to the above-referenced apparatus. Instead, the apparatus described above in reference to FIGS. 1-3 is a non-limiting example and the systems, articles of manufacture, methods, and/or computer program products of the present inventive subject matter may be applied to any system, article of manufacture, method, and/or computer program product in which pipette controls may be utilized, in which detecting a surface relative to a pipette may be desired, and/or in which determining a pipette position relative to a surface may be desired.

Reference is now made to FIG. 4, which is a perspective view of a pipette 80 according to some embodiments of the present inventive subject matter. In some embodiments, the pipette 80 may include a pipette tip 88 releasably attached to the pipette 80. In some embodiments, systems, articles of manufacture, methods, and/or computer program products of the present inventive subject matter may include a pipette pressure detector 82. The pipette pressure detector 82 may include a pressure transducer 84 and a pressure data module 86. In some embodiments, the pressure transducer 84 and pressure data module 86 may be integrated into a single package. In some embodiments, the pipette pressure detector 82 may be mounted onto the pipette 80 and/or may be integral to the pipette 80.

The pressure transducer 84 may be in fluidic communication with the pipette 80 and/or may be built-in to the pipette 80. The pressure data module 86 may receive and/or transmit signals corresponding to a pressure at an internal portion of the pipette 80. Some embodiments include the pressure data module 86 receiving signals from the pressure transducer 84. In some embodiments, the pressure data module 86 may convert a signal received from the pressure transducer 84 to a different signal and/or signal format, such as, for example, from an analog signal to a digital signal.

The pipette pressure detector 82 may measure pressure and/or vacuum profiles at an internal portion of a pipette. Example pipette pressure detectors that include a pipette include, but are not limited to, those commercially available from Tecan under the name CAVRO® and from Hamilton Company under the name ZEUS™. In some embodiments, the pipette pressure detector 82 may use real-time pressure data to detect a surface 90 and/or to determine a position of the pipette 80 and/or pipette tip 88 above a surface 90.

In some embodiments, the pipette pressure detector 82 may use pressure data to determine and/or verify dispensing of a fluid in the pipette tip 88 attached to the pipette 80. In some embodiments, the fluid is a liquid. Some embodiments include determining and/or verifying dispensing of a fluid from the pipette tip 88 attached to the pipette 80 after a given volume of fluid has been dispensed. In some embodiments, the pipette pressure detector may be used to determine and/or verify that a sufficient volume of liquid is/was present in the pipette tip 88 after a portion of the liquid was dispensed.

In some embodiments, the pipette pressure detector 82 may use pressure data to detect and/or determine the integrity of the pipette tip 88. In some embodiments, the pipette pressure detector 82 may use pressure data to determine that the pipette tip 88 is properly functioning and/or is suitable for use. In some embodiments, determining that the pipette tip 88 is suitable for use includes determining that that the pipette tip 88 attached to pipette 80 is suitable to aspirate and dispense a liquid. Some embodiments include using the pipette pressure detector to detect and/or determine that the pipette tip 88 is not functioning properly and/or is not suitable for use. Some embodiments include aspirating a gas into the pipette tip 88 while the pipette pressure detector 82 may be measuring pressure and/or vacuum profiles at an internal portion of the pipette 80 to determine whether the pipette tip 88 attached to pipette 80 is properly functioning and/or suitable for use.

In some embodiments, the pipette pressure detector 82 may use real-time pressure data to detect a droplet at the distal end of pipette tip 88 attached to pipette 80 and/or the formation of a droplet at the distal end of pipette tip 88 attached to a pipette 80. In some embodiments, the pipette pressure detector 82 may be used to detect a clog in the pipette tip 88. In some embodiments, the pipette pressure detector 82 may be used to detect an empty pipette tip (i.e., a pipette tip with no liquid present in the pipette tip).

The pipette pressure detector 82 may perform and/or be utilized in one or more operations of the methods and systems described below.

Reference is now made to FIG. 5, which is a flowchart illustrating operations of methods according to some embodiments of the present inventive subject matter. The methods may include positioning a pipette at a first distance above a surface using a first position detector at block 100 and positioning the pipette at a second distance above the surface using a second position detector at block 120, with the second position detector being different than the first position detector and the second distance being less than the first distance. Some embodiments include that the first position detector uses a first technology for determining a position, such as, for example an optical and/or ultrasonic position detector, among others. Some embodiments provide that the second position detector uses a second technology that is different than the first technology. The first and/or second distance may include a defined position above the surface and/or a position range above the surface.

In some embodiments, the second position detector may include a pipette pressure detector and the first position detector may use a metric other than pressure. The pipette pressure detector may include a pressure transducer and may measure pressure at an internal portion of a pipette. The pipette pressure detector may be as described above in reference to FIG. 4 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 5. In some embodiments, the pipette pressure detector may use real-time pressure data to detect the surface and/or determine the second distance. In some embodiments, the first position detector may include an optical position detector, such as, but not limited to, a camera, and/or an ultrasonic position detector, which may include a sensor. In some embodiments, the first position detector may be used to determine the distance to the surface and/or the surface of medium (e.g., agar) present a container, such as a plate.

Some embodiments include, prior to positioning the pipette at the second distance, contacting the surface with a tip of the pipette at block 110. In some embodiments, the tip of the pipette is the distal end of a pipette tip that is attached to the pipette (i.e., the end of the pipette tip farthest from the pipette).

Some embodiments include positioning the pipette at the first distance at block 100 at any suitable distance above the surface. In some embodiments, the first distance above the surface is a known distance, which may be determined using the first position detector. In some embodiments, the first distance may be greater than the degree of error in determining the surface with the first position detector. For example, if the first position detector has a degree of error off 0.5 mm in detecting the surface, then the first position may be at least greater than 0.5 mm above the surface, such as for example, in a range of 0.6 mm to 1 mm above the surface. In some embodiments, the first distance may be in a range of about 0.3 mm to about 40 cm above the surface, such as, for example, in a range of about 0.3 mm to about 1 mm, about 0.5 mm to about 1 mm, about 0.5 mm to about 5 cm, about 1 mm to about 10 cm, about 1 mm to about 1 cm, about 2 cm to about 10 cm, or about 10 cm to about 40 cm. In some embodiments, the first distance may be about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, or 9 mm above the surface or about 1, 2, 3, 4, 5 cm or more above the surface. The first distance values provided herein are examples and are not intended to limit the scope of the invention. For example, the first distance may be less than 0.3 mm or greater than 40 cm.

The second distance may be any suitable distance above the surface that is less than the first distance. In some embodiments, the second distance may be in a range of about 0.05 mm to about 1 cm above the surface, such as, for example, in a range of about 0.05 mm to about 5 mm, about 0.1 mm to about 1 mm, about 0.1 mm to about 0.5 mm, or about 1 mm to about 1 cm. In some embodiments, the second distance may be about 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm above the surface. The second distance values provided herein are examples and are not intended to limit the scope of the invention. For example, the second distance may be less than 0.05 mm or greater than 1 cm.

Some embodiments include positioning the distal end of a pipette tip attached to the pipette at the first distance and/or second distance. In some embodiments, the first and/or second distance may vary depending on the liquid sample type and/or the surface type (e.g., the type of the growth culture medium). In some embodiments, the surface may not be level and/or may not include uniform surface characteristics.

In some embodiments, the second position detector may improve the accuracy of determining the location of and/or distance to the surface and/or detecting the surface. Some embodiments include the second position detector positioning the pipette and/or detecting the surface with an accuracy in a range of ± about 0.03 mm to about 0.1 mm, such as, for example, about 0.03 mm to about 0.05 mm or about 0.04 mm to about 0.06 mm. In some embodiments, the second position detector positions the pipette and/or detects the surface with an accuracy of about 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 mm. The accuracy values provided herein for the second position detector are examples and are not intended to limit the scope of the invention. For example, the accuracy for the second position detector may be less than 0.03 mm or greater than 0.1 mm. In some embodiments, the second position detector determines and/or detects the surface at a position where or close to where the pipette may initially dispense a liquid from an attached pipette tip, such as, for example, at a position in the x- and/or y-direction where the pipette will dispense the liquid.

Reference is now made to FIG. 6, which is a flowchart illustrating operations of methods according to some embodiments of the present inventive subject matter. In some embodiments, the methods may include measuring a pipette pressure at an internal portion of a pipette at block 200. In some embodiments, measuring a pipette pressure at an internal portion of a pipette at block 200 may include generating a plurality of pipette pressure values. In some embodiments, measuring the pipette pressure at an internal portion of the pipette at block 200 is carried out using a pipette pressure detector including a pipette as described above in reference to FIG. 4, the duplicate discussion of the pipette pressure detector and pipette is omitted herein for the purposes of discussing FIG. 6. Some embodiments include measuring the pipette pressure at block 200 with a liquid and/or a gas in a pipette tip attached to the pipette.

Measuring the pipette pressure at block 200 may include measuring the pipette pressure at given time intervals. Any suitable time interval may be used to measure the pipette pressure. In some embodiments, the time interval may depend on whether the pipette and/or surface is/are moving and, if so, the rate of movement and/or the time interval may depend on whether gas is being aspirated into the pipette and, if so, the rate of aspiration. Some embodiments include measuring the pipette pressure at block 200 every 0.1 to 100 milliseconds, such as, for example, every 1 to 50, 0.1 to 10, 1 to 10, 10 to 50, or 50 to 100 milliseconds. In some embodiments, pipette pressure at block 200 is measured every 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, or more milliseconds. The given time intervals provided herein are examples and are not intended to limit the scope of the invention. For example, the pipette pressure may be measured at time intervals less than 0.1 milliseconds or greater than 100 milliseconds.

In some embodiments, measuring the pipette pressure at block 200 includes measuring the pipette pressure while aspirating gas into a pipette tip attached to the pipette and/or while the pipette is moving toward a surface and/or the surface is moving toward the pipette. Some embodiments include aspirating a gas into a pipette tip attached the pipette. The gas may be aspirated at any suitable flow rate. In some embodiments, the flow rate may depend on the sample type including the sample viscosity and/or if the pipette tip includes a filter. In some embodiments, the gas may be aspirated into the pipette tip at a constant flow rate. Some embodiments include aspirating a gas at a flow rate in a range of about 1 μL/s to about 100 mL/s, such as, for example, in a range of about 1 μL/s to about 100 μL/s, about 5 μL/s to about 40 μL/s, or about 1 mL/s to about 100 mL/s. In some embodiments, a gas may be aspirated at a flow rate of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100 μL/s or more. The flow rates provided herein for aspirating a gas are examples and are not intended to limit the scope of the invention. For example, the flow rate for aspirating a gas may be less than 1 μL/s or greater than 100 mL/s. Some embodiments include measuring the pipette pressure at block 200 while aspirating gas into a pipette tip attached to the pipette and while the pipette is moving toward a surface.

In some embodiments, measuring the pipette pressure at block 200 includes measuring the pipette pressure while the pipette is moving toward a surface. The pipette may move toward the surface in any direction. In some embodiments, the pipette may move downward in a z-direction toward the surface. Some embodiments include the pipette moving toward the surface at any suitable rate. In some embodiments, the pipette may move toward the surface, such as, for example, downward in the z-direction, at a rate in a range of about 0.1 mm/s to about 10 mm/s, such as, for example, in a range of about 0.5 mm/s to about 7 mm/s, about 1 mm/s to about 10 mm/s, or about 1 mm/s to about 5 mm/s. In some embodiments, the pipette may move toward the surface, such as, for example, downward in the z-direction, at a rate of about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm/s or more. The rates of movement for a pipette provided herein are examples and are not intended to limit the scope of the invention. For example, the rate of movement may be less than 0.1 mm/s or greater than 10 mm/s.

In some embodiments, measuring the pipette pressure at block 200 includes measuring the pipette pressure while the surface is moving toward the pipette. The surface may move toward the pipette in any direction. In some embodiments, the surface may move upward in a z-direction toward the pipette. Some embodiments include the surface moving toward the pipette at any suitable rate. In some embodiments, the surface may move toward the pipette, such as, for example, upward in the z-direction, at a rate in a range of about 0.1 mm/s to about 10 mm/s, such as, for example, in a range of about 0.5 mm/s to about 7 mm/s, about 1 mm/s to about 10 mm/s, or about 1 mm/s to about 5 mm/s. In some embodiments, the surface may move toward the pipette, such as, for example, upward in the z-direction, at a rate of about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm/s or more. The rates of movement for a surface provided herein are examples and are not intended to limit the scope of the invention. For example, the rate of movement may be less than 0.1 mm/s or greater than 10 mm/s.

Referring again to FIG. 6, some embodiments include determining a pressure difference relative to a previously measured pipette pressure value at block 210. In some embodiments, any previously measured pipette pressure value may be used to determine the pressure difference at block 210. In some embodiments, the pressure difference may be determined using the most recently pipette pressure value and the pipette pressure value measured immediately preceding the most recently measured pipette pressure value. Some embodiments include subtracting the previously measured pipette pressure value from the most recently measured pipette pressure value to obtain the pressure difference at block 210.

Some embodiments include estimating a rate of change in pipette pressure at block 220. In some embodiments, estimating the rate of change in pipette pressure at block 220 includes mathematically weighting the pressure difference determined at block 210 to provide a weighted pressure difference. Weighting may include multiplying an original value by a given weighting factor to provide a weighted value. In some embodiments, estimating the rate of change in pipette pressure at block 220 includes summing the weighted pressure difference with a weighted previously calculated rate of change in pipette pressure. In some embodiments, the weighted previously calculated rate of change in pipette pressure may be estimated using the pipette pressure value immediately preceding the most recently measured pipette pressure value. Some embodiments include weighting the pressure difference by about 0% to 49% and weighting the previously calculated rate of change in pipette pressure by about 51% to about 100%. In some embodiments, the pressure difference may be weighted by about 5% to 25% and the previously calculated rate of change in pipette pressure may be weighted by about 75% to about 95%. In some embodiments, weighting the pressure difference and/or the previously calculated rate of change in pipette pressure may function as a single-pole filter or the rate of change data.

In some embodiments, estimating the rate of change in pipette pressure at block 220 includes estimating the rate of change in pipette pressure using the following equation: Rate of change in pipette pressure=(X·P _(n))+(Y·P _(n-1)), in which X is a first weighting factor, Y is a second weighting factor, P_(n) is a most recently estimated pressure difference value, and P_(n-1) is the pressure difference value immediately preceding P_(n), the most recently estimated pressure difference value. In some embodiments, the first weighting factor and the second weighting factor may be the same or different.

Some embodiments include estimating a statistical variable at block 230. In some embodiments, the statistical variable corresponds to the rate of change in pipette pressure estimated at block 220. In some embodiments, estimating the statistical variable at block 230 includes estimating an average rate of change in pipette pressure. In some embodiments, estimating the statistical variable at block 230 includes estimating a ratio relating to the rate of change in pipette pressure. The ratio relating to the rate of change in pipette pressure may include the rate of change in pipette pressure and the average rate of change in pipette pressure.

For example, in some embodiments, estimating the statistical variable at block 230 may be expressed using the following equation:

Average rate of change in pipette pressure=(P₁+P₂+ . . . P_(n))/n, in which P₁, P₂, and P_(n) are each pressure difference values with P_(n) being the most recently estimated pressure difference value, and n is the total number of pipette pressure values measured. Thus, in some embodiments, the average rate of change in pipette pressure is obtained by taking the sum of all the pressure difference values estimated divided by the total number of pipette pressure values measured. In some embodiments, P₁, P₂, and P_(n) may each independently be weighted pressure difference values. In some embodiments, the average rate of change in pipette pressure is obtained by taking the sum of all the pipette pressure values measured divided by the total number of pipette pressure values measured. In some embodiments, the average rate of change in pipette pressure may correspond to an average taken over the entire sampling period, whereas some embodiments may provide that the average is a moving average taken over only a portion of the sampling period.

In some embodiments, estimating the statistical variable at block 230 may be expressed using the following equation: Ratio relating to the rate of change in pipette pressure=absolute value(P _(n) /P _(average)), in which P_(n) is the most recently estimated pressure difference value and P_(average) is the average pipette pressure. In some embodiments, P_(n) may be a weighted pipette difference value. In some embodiments, the average pipette pressure may be determined as described above in regard to the average rate of change in pipette pressure.

Some embodiments include comparing the statistical variable to a pipette pressure related threshold at block 240. Some embodiments include two or more pipette pressure related thresholds, such as, for example, 2, 3, 4, 5 or more pipette pressure related thresholds. Some embodiments include a pipette pressure related threshold that may depend on and/or be tuned based on the pipette, the volume of fluid (i.e., liquid and/or gas) present in a pipette tip, the rate of aspiration or dispense, and/or the fluid type and/or properties thereof. In some embodiments, a pipette pressure related threshold may be empirically determined.

In some embodiments, the pipette pressure related threshold may be determined using any suitable rate of aspiration and/or rate of movement. In some embodiments, the pipette pressure related threshold may be determined with a rate of aspiration in a range of about 1 μL/s to about 100 mL/s, such as, for example, in a range of about 1 μL/s to about 100 μL/s, about 5 μL/s to about 40 μL/s, or about 1 mL/s to about 100 mL/s. In some embodiments, the pipette pressure related threshold may be determined with a rate of aspiration of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100 μl/s or more. The rates of aspiration for determining a pipette pressure related threshold provided herein are examples and are not intended to limit the scope of the invention. For example, the rate of aspiration for determining a pipette pressure related threshold may be less than 1 μL/s or greater than 100 mL/s. The rate of aspiration may be the rate at which a gas is aspirated into a pipette tip attached to a pipette. In some embodiments, the pipette pressure related threshold is determined with a rate of aspiration that is the same as the rate at which a pipette aspirates gas into a pipette tip while the pipette pressure is being measured at block 200.

In some embodiments, the pipette pressure related threshold may be determined with a rate of movement in a range of about 0.1 mm/s to about 10 mm/s, such as, for example, in a range of about 0.5 mm/s to about 7 mm/s, about 1 mm/s to about 10 mm/s, or about 1 mm/s to about 5 mm/s. In some embodiments, the pipette pressure related threshold may be determined with a rate of movement of about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm/s or more. The rates of movement for determining a pipette pressure related threshold provided herein are examples and are not intended to limit the scope of the invention. For example, the rate of movement for determining a pipette pressure related threshold may be less than 0.1 mm/s or greater than 10 mm/s. In some embodiments, the pipette pressure related threshold is determined with a rate of movement that is the same as the rate at which a pipette moves toward a surface, such as downward in the z-direction toward a surface, while the pipette pressure is being measured at block 200. Some embodiments include determining the pipette pressure related threshold when the pipette is moving downward in the z-direction toward the surface.

Referring again to FIG. 6, comparing the statistical variable to the pipette pressure related threshold at block 240 may include using two or more pipette pressure related thresholds. In some embodiments, a first value may be compared to a first pressure related threshold and the statistical variable may be compared to a second pressure related threshold. In some embodiments, the first value may be a rate of change in pipette pressure and the statistical variable may be a ratio of the rate of change in pipette pressure divided by an average rate of change in pipette pressure. In some embodiments, the statistical variable may the absolute value of the ratio of the rate of change in pipette pressure divided by an average rate of change in pipette pressure. In some embodiments, the rate of change in pipette pressure may be estimated at block 220 and the ratio may be estimated at block 230. In some embodiments, the first pressure related threshold may be a rate of change in pipette pressure threshold and the second pressure related threshold may be a pipette pressure ratio threshold. Some embodiments include determining and/or detecting contact with a surface at block 260 when the rate of change in pipette pressure is less than or equal to the rate of change in pipette pressure threshold and the ratio of the rate change in pipette pressure divided by the average rate of change in pipette pressure is greater than or equal to the pipette pressure ratio threshold.

Some embodiments include estimating a pipette position at block 250. Estimating the pipette position at block 250 may include estimating the position of a pipette tip relative to a surface. In some embodiments, estimating the pipette position at block 250 includes determining and/or detecting contact with a surface at block 260. Some embodiments include determining that a surface is not in contact with the pipette at block 260 and, responsive to determining that the surface is not in contact with the pipette, continuing to estimate the pipette position. Continuing to estimate the pipette position may include repeating one or more operations described in FIG. 6.

In some embodiments, estimating the pipette position at block 250 includes determining that a surface is in contact with the pipette at block 260. In some embodiments, determining that the surface is in contact with the pipette at block 260 includes determining that the distal orifice of a pipette tip attached to the pipette begins to seal and/or has sealed with the surface. In some embodiments, determining that the surface is in contact with the pipette at block 260 includes detecting at least two consecutive data points (e.g., 2, 3, 4, 5, or more consecutive data points) that indicate contact to the surface with the pipette. The at least two consecutive data points may indicate the point at which the distal orifice of a pipette tip attached to the pipette begins to seal and/or has sealed with the surface.

In some embodiments, determining that the surface is in contact with the pipette at block 260 includes detecting an inflection point in the pipette pressure data obtained by measuring the pipette pressure over a given period of time. The inflection point may be the point at which a pipette tip attached to the pipette contacts the surface and/or the point at which the distal orifice of a pipette tip attached to the pipette begins to seal and/or has sealed with the surface. Referring briefly to FIG. 7, which is a graph of pressure values versus time according to some embodiments of the present inventive subject matter, in some embodiments, the inflection point may be a point preceding a drop or decrease in pressure value. Some embodiments may include a significant drop or decrease in pressure value after the inflection point. In some embodiments, the pressure values prior to the inflection point may increase in value.

Referring again to FIG. 6, some embodiments include, responsive to determining that the surface is in contact with the pipette, stopping the movement of the pipette and/or surface and/or adjusting the position of the pipette and/or surface so that the pipette is at a defined position above the surface. In some embodiments, movement of the pipette toward the surface is stopped and the pipette is moved to a defined position above the surface. In some embodiments, movement of the surface toward the pipette is stopped and the surface is moved to a defined position below the pipette.

Some embodiments include, responsive to determining that the surface is in contact with the pipette, stopping the aspiration of gas.

Some embodiments include detecting a positioning error at block 270. In some embodiments, detecting a positioning error at block 270 may be responsive to determining that the pipette is not in contact with a surface at block 260. In some embodiments, detecting a positioning error at block 270 may be responsive to a given distance moved by the pipette and/or surface.

In some embodiments, detecting a positioning error at block 270 may include comparing the rate of change in pipette pressure to a pressure error threshold. In some embodiments, detecting a positioning error at block 270 may include determining that the rate of change in pipette pressure is less than or equal to the pressure error threshold. Some embodiments may include two or more pressure error thresholds, such as, for example, 2, 3, 4, 5 or more pressure error thresholds. In some embodiments, the pressure error threshold may be determined using any suitable rate of aspiration and/or rate of movement, such as those described above in regard to the pipette pressure related threshold, the duplicate discussion thereof may be omitted herein. Some embodiments include a pressure error threshold that may depend on and/or be tuned based on the pipette, the volume of fluid (i.e., liquid and/or gas) present in a pipette tip, the rate of aspiration or dispense, and/or the fluid type and/or properties thereof. In some embodiments, a pressure error threshold may be empirically determined.

In some embodiments, detecting a positioning error at block 270 may include detecting at least two consecutive data points that indicate the positioning error has occurred. Some embodiments may include detecting 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or more consecutive data points that indicate the positioning error has occurred.

In some embodiments, detecting a positioning error at block 270 may include detecting a clog in the pipette tip. In some embodiments, detecting a positioning error at block 270 may include failing to detect a surface. In some embodiments, failing to detect the surface may result in the pipette tip being at a position past the surface. In some embodiments, a clog in the pipette tip may be caused by the pipette failing to detect the surface and the pipette tip going into the surface (e.g., solid growth culture medium, such as agar) and/or aspirating a portion of the surface.

Reference is now made to FIG. 8, which is a flowchart illustrating operations of methods according to some embodiments of the present inventive subject matter. In some embodiments, the methods may include measuring a pipette pressure at an internal portion of a pipette having a pipette tip attached thereto, while the pipette is aspirating gas into the pipette tip and while the pipette and/or surface is/are moving at block 200 a. In some embodiments, measuring the pipette pressure at an internal portion of a pipette having a pipette tip attached thereto at block 200 a includes generating a plurality of pipette pressure values. Certain aspects of the operation at block 200 a have been described above in regard to block 200 in FIG. 6 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 8. In some embodiments, the method may include determining a pressure difference relative to a previously measured pipette pressure value at block 210, estimating a rate of change in pipette pressure at block 220, estimating a statistical variable at block 230, and/or comparing the statistical variable to a pressure related threshold at block 240, each as described above in regard to FIG. 6.

Some embodiments include determining if the surface is in contact and/or has been contacted with the pipette tip at block 260 a. Certain aspects of the operation at block 260 a have been described above in regard to block 260 in FIG. 6 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 8. In some embodiments, determining if the surface has been contacted with the pipette tip at block 260 a is responsive to the comparing step at block 240. In some embodiments, determining if the surface is in contact and/or has been contacted with the pipette tip at block 260 a includes estimating the position of the pipette tip relative to the surface.

Referring again to FIG. 8, some embodiments include, responsive to determining that the surface is in contact with the pipette tip at block 260 a, detecting a positioning error at block 270. Certain aspects of the operation at block 270 have been described above in regard to block 270 in FIG. 6 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 8.

As shown in FIG. 8, some embodiments include, responsive to determining that the surface is in contact with the pipette tip at block 260 a, stopping the movement of the pipette and/or surface and the aspiration of gas into the pipette tip at block 280. In some embodiments, movement of the pipette toward the surface is stopped. Some embodiments include, responsive to stopping movement of the pipette toward the surface, moving the pipette to a defined position above the surface. In some embodiments, movement of the surface toward the pipette is stopped. Some embodiments include, responsive to stopping movement of the surface toward the pipette, moving the surface to a defined position below the pipette.

Reference is now made to FIG. 9, which is a flowchart illustrating operations of methods according to some embodiments of the present inventive subject matter. In some embodiments, methods may include aspirating a liquid into a pipette tip attached to a pipette at block 300. The liquid may be any suitable liquid. In some embodiments, the liquid may be a biological sample. Any suitable volume of the liquid may be aspirated into the pipette tip. In some embodiments, the volume of liquid may be a sufficient volume such that at least a portion of the volume is dispensed onto the surface of the target. Any suitable pipette tip may be releasably attached to the pipette. In some embodiments, the pipette tip may include a filter.

Some embodiments include positioning the pipette tip at a first distance above a surface at block 305. The first distance may be any suitable distance above the surface. In some embodiments, the first distance above the surface is a known distance, which may be determined using any devices and/or methods known to those of skill in the art. In some embodiments, the first distance may be determined using an optical position detector and/or an ultrasonic position detector, as described above. In some embodiments, the first distance may be in a range of about 0.3 mm to about 40 cm above the surface, such as, for example, in a range of about 0.3 mm to about 1 mm, about 0.5 mm to about 1 mm, about 0.5 mm to about 5 cm, about 1 mm to about 10 cm, about 1 mm to about 1 cm, about 2 cm to about 10 cm, or about 10 cm to about 40 cm. In some embodiments, the first distance may be about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, or 9 mm above the surface or about 1, 2, 3, 4, 5 cm or more above the surface. The first distance values provided herein for positioning a pipette tip above a surface are examples and are not intended to limit the scope of the invention. For example, the first distance may be less than 0.3 mm or greater than 40 cm.

Some embodiments include moving the pipette toward the surface while aspirating gas into the pipette tip at block 310. The movement of the pipette and aspiration of gas, including the rate of movement of the pipette toward the surface and the rate of aspiration of gas into the pipette tip, may be as described above in reference to FIG. 6 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 9. Some embodiments include moving the liquid in the pipette tip to closer to the proximal end of the pipette tip as the pipette moves toward the surface and aspirates gas into the pipette tip at block 310. In some embodiments, pipette pressure may be measured at an internal portion of the pipette at block 320 while the pipette is moving toward the surface and aspirating gas into the pipette tip.

In some embodiments, prior to aspirating the liquid into the pipette tip at block 300, a first volume of gas may be aspirated into the pipette tip. A second volume of gas may also be aspirated into the pipette tip. In some embodiments, prior to moving the pipette toward the surface while aspirating gas into the pipette tip at block 310, a volume of gas may be aspirated into the pipette tip. Accordingly, in some embodiments, the pipette tip may include, from the proximal to distal end of the pipette tip, a first volume of gas, the liquid, and a second volume of gas. In some embodiments, if the second volume of gas is present, then as the pipette moves toward the surface while aspirating gas into the pipette tip at block 310 the second volume of gas may increase in volume.

In some embodiments, the pipette pressure data may be collected at block 325. The pipette pressure data may include a plurality of pipette pressure values that may be obtained and/or generated by measuring the pipette pressure at an internal portion of the pipette. Some embodiments include storing the collected pipette pressure data for a given period of time. In some embodiments, the pipette pressure data may be stored until contact with the surface is detected.

Some embodiments include using the pipette pressure data to detect contact to the surface with the pipette tip at block 330. Detecting contact to the surface at block 330 may be as described above in reference to FIGS. 6 and 8 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 9. In some embodiments, detecting contact to a surface at block 330 may include determining a pressure difference relative to a previously measured pipette pressure value, estimating a statistical variable corresponding to a rate of change in pipette pressure, comparing the statistical variable to a pipette pressure related threshold, and/or responsive to comparing the statistical variable to the pipette pressure related threshold, estimating a pipette position, each as described in reference to FIGS. 6 and 7.

Referring again to FIG. 9, some embodiments include stopping the movement of the pipette toward the surface and the aspiration of gas into the pipette tip at block 340. For example, movement may be stopped responsive to detecting contact between the pipette tip and the surface.

Some embodiments include moving the pipette to a given position above the surface at block 350. The pipette may be moved to any suitable position above the surface. In some embodiments, the position above the surface may vary depending on the liquid sample type and/or the surface type (e.g., the type of the growth culture medium). In some embodiments, the position may be determined to improve the chances of the sample being wicked onto the surface and/or to reduce the risk of a false negative. In some embodiments, the position may be such that the distal end of a pipette tip attached to the pipette is in a range of about 0.05 mm to about 1 cm above the surface, such as, for example, in a range of about 0.05 mm to about 5 mm, about 0.1 mm to about 1 mm, about 0.1 mm to about 0.5 mm, or about 1 mm to about 1 cm. In some embodiments, the position may be such that the distal end of a pipette tip attached to the pipette is about 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm above the surface. The positions provided herein for the distal end of a pipette tip attached to the pipette relative to a surface are examples and are not intended to limit the scope of the invention. For example, the position of the distal end of a pipette tip attached to the pipette above a surface may be less than 0.05 mm or greater than 1 cm.

Reference is now made to FIG. 10, which is a flowchart illustrating operations in systems according to some embodiments of the present inventive subject matter. The operations in the systems may include measuring a pipette pressure at an internal portion of a pipette at block 400, determining a pressure difference relative to a previously measured pipette pressure value at block 410, estimating a rate of change in pipette pressure at block 420, estimating a statistical variable at block 430, comparing the statistical variable to a pipette pressure related threshold at block 440, and/or estimating a pipette position based on the results of the comparing at block 450. Each of these operations may be as described above in reference to FIGS. 6 and 8 and duplicate discussion thereof may be omitted herein for the purpose of discussing FIG. 10.

In some embodiments, responsive to estimating a pipette position at block 450, it may be determined if contact with a surface has been detected at block 460. If no contact with the surface has been detected at block 460, then the system may continue to perform one or more of the operations described in FIG. 10 to determine if contact with the surface is subsequently detected.

In some embodiments, if no contact with the surface has been detected at block 460, then the system may determine if a positioning error is detected at block 480. If no positioning error is detected at block 480, then the system may continue to perform one or more of the operations described in FIG. 10 to determine if contact with the surface is subsequently detected. If a positioning error is detected at block 480, then the system may report the positioning error at block 485 and may stop the operations at blocks 400, 410, 420, 430, 440, and 450.

If contact with the surface has been detected at block 460, then the system may stop performing the operations. Some embodiments include detecting contact with the surface at block 460 and stopping the operations at blocks 400, 410, 420, 430, 440, and 450. In some embodiments, responsive to detecting contact with the surface at block 460, the system may move the pipette to a given position above the surface at block 470.

During one or more operations described in regard to FIG. 10, the system may be acting at one or more of the same and/or different operations. In some embodiments, one or more operations may be occurring at any given time.

Reference is now made to FIG. 11, which is a block diagram illustrating a system 500 according to some embodiments of the present inventive subject matter. The system may include a processor 510, a memory 512, a network interface 514, a pipette 530, a pipette pressure detector 540, a pressure transducer 542, and pressure data module 544.

The processor 510 may be configured to execute computer program code from memory 512, described below as a computer readable storage medium, to perform at least some of the operations and methods described herein, and may be any conventional processor(s), including, but not limited to the AMD Athlon™ 64, or Intel® Core™ Duo, among others. The memory 512 may be coupled to the processor 510 and may include computer readable program code embodied therein that, when executed by the processor 510, may cause the processor 510 to receive, generate, store, and/or transmit information relating to an internal pressure in the pipette 530 and/or the location of the pipette 530 (e.g., if the pipette is in contact with a surface) and/or a condition of a pipette tip (e.g., pipette tip integrity, if a pipette tip is functioning properly, dispensing of a fluid from a pipette tip, if a droplet is at the distal end of the pipette tip, if the pipette tip is clogged, and/or if the pipette tip is empty).

In some embodiments, the pipette 530 may include a pipette tip, which may be releasably attached to the pipette 530. The pipette 530 may be in electronic communication with the processor 510. The pipette pressure detector 540 may include a pressure transducer 542 and a pressure data module 544. In some embodiments, the pressure transducer 542 and pressure data module 544 may be integrated into a single package. In some embodiments, the pipette pressure detector 540 may be mounted onto the pipette 530 and/or may be integral to the pipette 540.

The pressure transducer 542 may be in fluidic communication with the pipette 530 and/or may be built-in to the pipette 530. In some embodiments, the pressure transducer 542 may measure pressure and/or vacuum profiles at an internal portion of a pipette 530. The pressure transducer 542, pipette pressure detector 540, and/or pipette 530 may transmit real-time pressure data to the processor 510 and/or pressure data module 544 that may be communicatively coupled to the processor 510. The real-time pressure data may be used to detect a surface and/or to determine a position of the pipette 530 and/or a pipette tip attached to the pipette 530. The pressure data module 544 may receive and/or transmit signals corresponding to a pressure at an internal portion of the pipette 530. Some embodiments include the pressure data module 544 receiving signals from the pressure transducer 542. In some embodiments, the pressure data module 544 may convert a signal received from the pressure transducer 542 to a different signal and/or signal format, such as, for example, from an analog signal to a digital signal. In some embodiments, the pressure data module 544 may transmit signals to the processor 510. In some embodiments, the pipette 530, pipette pressure detector 540, pressure data module 544, and/or pressure transducer 542 may be programmable. The pipette 530, pipette pressure detector 540, pressure data module 544, and/or pressure transducer 542 may perform and/or be utilized in one or more operations of the methods and systems described above.

As will be appreciated by one skilled in the art, aspects of the present disclosure may be illustrated and described herein in any of a number of patentable classes or context including any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof. Accordingly, aspects of the present disclosure may be implemented entirely hardware, entirely software (including firmware, resident software, micro-code, etc.) or combining software and hardware implementation that may all generally be referred to herein as a “circuit,” “module,” “component,” or “system.” Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable media having computer readable program code embodied thereon.

Any combination of one or more computer readable media may be utilized. The computer readable media may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an appropriate optical fiber with a repeater, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python or the like, conventional procedural programming languages, such as the “C” programming language, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, dynamic programming languages such as Python, Ruby and Groovy, or other programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider) or in a cloud computing environment or offered as a service such as a Software as a Service (SaaS).

Aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatuses (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable instruction execution apparatus, create a mechanism for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that when executed can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions when stored in the computer readable medium produce an article of manufacture including instructions which when executed, cause a computer to implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable instruction execution apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatuses or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

Some embodiments provide that one or more of the programs may be executed during a portion of execution of another one of the programs in the corresponding process operation.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various aspects of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The term “about,” as used herein when referring to a measurable value, such as an amount or distance and the like, is meant to refer to variations of up to ±20% of the specified value, such as, but not limited to, ±10%, ±5%, ±1%, ±0.5%, or even ±0.1% of the specified value, as well as the specified value. For example, “about X” where X is the measurable value, is meant to include X as well as variations of ±20%, ±10%, ±5%, ±1%, ±0.5%, or even ±0.1% of X. A range provided herein for a measurable value may include any other range and/or individual value therein.

The corresponding structures, materials, acts, and equivalents of any means or step plus function elements in the claims below are intended to include any disclosed structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The aspects of the disclosure herein were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. A method comprising: measuring a pipette pressure at an internal portion of a pipette to generate a plurality of pipette pressure values; determining a pressure difference relative to at least one previously measured pipette pressure value; estimating a rate of change in pipette pressure, wherein estimating the rate of change in pipette pressure comprises weighting the pressure difference to provide a weighted pressure difference; estimating at least one statistical variable corresponding to the rate of change in pipette pressure; comparing the at least one statistical variable to at least one pipette pressure related threshold; and responsive to comparing the at least one statistical variable to the at least one pipette pressure related threshold, estimating a pipette position.
 2. The method of claim 1, wherein estimating the rate of change in pipette pressure comprises summing the weighted pressure difference with at least one weighted previously calculated rate of change in pipette pressure.
 3. The method of claim 1, wherein measuring the pipette pressure comprises measuring the pipette pressure with a liquid and/or gas in a pipette tip attached to the pipette.
 4. The method of claim 1, wherein measuring the pipette pressure comprises measuring the pipette pressure while aspirating gas into a pipette tip attached to the pipette and while the pipette is moving toward a surface and/or the surface is moving toward the pipette.
 5. The method of claim 4, wherein the pipette aspirates gas at a constant flow rate.
 6. The method of claim 1, wherein estimating the at least one statistical variable comprises estimating an average rate of change in pipette pressure.
 7. The method of claim 1, wherein estimating the at least one statistical variable comprises estimating a ratio relating to the rate of change in pipette pressure.
 8. The method of claim 7, wherein the ratio relating to the rate of change in pipette pressure includes the rate of change in pipette pressure and the average rate of change in pipette pressure.
 9. The method of claim 1, wherein comparing the at least one statistical variable comprises comparing the rate of change in pipette pressure to a first pressure related threshold and comparing the at least one statistical variable to a second pressure related threshold.
 10. The method of claim 9, wherein the at least one statistical variable is a ratio of the rate of change in pipette pressure divided by an average rate of change in pipette pressure, wherein the first pressure related threshold is a rate of change in pipette pressure threshold and the second pressure related threshold is a pipette pressure ratio threshold, and wherein contact with a surface is detected when the rate of change in pipette pressure is less than or equal to the rate of change in pipette pressure threshold and the ratio of the rate change in pipette pressure divided by the average rate of change in pipette pressure is greater than or equal to the pipette pressure ratio threshold.
 11. The method of claim 1, wherein estimating the pipette position comprises estimating the position of a pipette tip relative to a surface.
 12. The method of claim 1, wherein estimating the pipette position comprises determining that a surface is not in contact with the pipette and, responsive to determining that the surface is not in contact with the pipette, continuing to estimate the pipette position.
 13. The method of claim 1, wherein estimating the pipette position comprises determining that a surface is in contact with the pipette.
 14. The method of claim 13, wherein determining that the surface is in contact with the pipette comprises determining if the distal orifice of a pipette tip attached to the pipette has sealed with the surface.
 15. The method of claim 13, wherein determining that the surface is in contact with the pipette comprises detecting at least two consecutive data points that indicate contact to the surface with the pipette.
 16. The method of claim 13, further comprising, responsive to determining that the surface is in contact with the pipette, stopping movement of the pipette toward the surface and adjusting the pipette to a position above the surface, or responsive to determining that the surface is in contact with the pipette, stopping movement of the surface toward the pipette and adjusting the surface to a position below the pipette.
 17. The method of claim 1, further comprising detecting a positioning error, wherein detecting the positioning error comprises comparing the rate of change in pipette pressure to at least one pressure error threshold.
 18. The method of claim 1, wherein estimating the rate of change in pipette pressure comprises mathematically weighting the pressure difference to provide the weighted pressure difference.
 19. The method of claim 1, wherein a pipette pressure value in the plurality of pipette pressure values comprises an analog signal.
 20. The method of claim 1, wherein a pipette pressure value in the plurality of pipette pressure values comprises a digital signal.
 21. A computer system, comprising: a processor; and a memory coupled to the processor, the memory comprising computer readable program code embodied therein that, when executed by the processor, causes the processor to perform any of the operations of the method of claim
 1. 22. A computer program product comprising: a non-transitory computer readable storage medium having computer readable code embodied in the medium, the computer code comprising: computer readable code to perform operations of the method of claim
 1. 